This invention relates to a valve arrangement, and particularly to a control valve for use in controlling the operation of a fuel injector or other valve.
FIG. 1 illustrates a fuel injection nozzle comprising a generally cylindrical nozzle body 10 having a bore within which a valve needle 12 is slidable. The valve needle 12 includes a region 12a which is engageable with a seating provided in the body 10 to control the flow of fuel to small apertures 14. The body 10 includes an annular gallery 16 arranged to be supplied with fuel through a supply line 18, the needle 12 including a fluted region 12b permitting fuel to flow from the gallery towards the seating.
The needle 12 is biased towards the seating by a spring 20 provided within a spring chamber 22, the spring chamber 22 being supplied with fuel from the supply line 18 through a restricter 24. The spring chamber 22 communicates with a chamber 26 provided in a distance piece 28, a tubular valve member 30 forming part of a control valve arrangement being slidable with respect to the distance piece 28 under the influence of a solenoid actuator arrangement 32 including a spring arranged to bias the valve member 30 into engagement with a seating defined by a second distance piece 34. A cap nut 36 secures the body 10 and first and second distance pieces 28, 34 to a nozzle holder 38 in which the solenoid actuator arrangement 32 is housed.
In use, the supply line 18 is connected to a source of high pressure fuel, the fuel acting against the angled surfaces of the valve needle 12 tending to lift it from the seating against the action of the spring 20 and the pressure of fuel in the spring chamber 22. In the position illustrated in FIG. 1, the spring 20 and pressure of fuel in the spring chamber 22 are sufficient to maintain the valve needle 12 in engagement with the seating.
In order to commence injection, the solenoid actuator arrangement 32 is energized to lift the valve member 30 away from the second distance piece 34. Such movement permits fuel to flow from the spring chamber 22 and chamber 26 through the valve member 30 to a suitable drain. The reduction in fuel pressure in the spring chamber 22 results in a condition being reached in which the combined effect of the spring 20 and fuel pressure within the spring chamber 22 is insufficient to maintain the engagement between the valve needle 12 and seating, whereon fuel is permitted to flow past the seating and through the outlets 14.
To terminate injection, the solenoid actuator arrangement 32 is de-energized, the spring thereof returning the valve member 30 to the position illustrated in FIG. 1. Such movement results in the fuel pressure within the spring chamber 22 increasing, and in due course in the effect of the spring 20 and the pressure of fuel within the spring chamber 22 being sufficient to move the valve needle 12 into engagement with the seating.
It has been found that the control valve member 30 is relatively difficult to produce, slight inaccuracies in production resulting in poor injector performance. In addition, in use, damage to the valve member 30 and second distance piece 34 tends to occur, damage to the valve member 30 possibly resulting in a tendency for the valve member 30 to be lifted from the second distance piece 34 on the application of high pressure thereto.
Although the above description is of the use of the valve arrangement in a fuel injector, the valve arrangement may be used in other applications.